Headphone Output Quality?

I'd love to hear from any of the lucky folks who managed to get a handset already - how is the headphone output? I've seen all the great things about the speakers already, but haven't seen any reviews of the audio jack output.

I use pretty high-grade IEMs (Shure SE530) so a decent output from FLAC files is very important to me.

Well, I will hopefully be finding out for myself on Monday, when my order from unlocked-mobiles.com is scheduled to arrive. I will post back once I have it, but would still welcome any input from anyone who already has the device.